The present invention relates to processes for preparing hydrogenated C9 petroleum resins and hydrogenated C9 petroleum resins obtainable by said processes.
Conventionally, C9 petroleum resins are prepared by polymerizing C9 fractions obtained by naphtha cracking or the like, in the presence of a phenol (a molecular weight modifier) using a boron trifluoride phenol complex (a Friedel-Crafts catalyst). Hydrogenated C9 petroleum resins are obtained by hydrogenating the C9 petroleum resins under pressure, and because of their good initial color, tack, adhesion and high compatibility with other resins, hydrogenated C9 petroleum resins are mixed and melted with various plastics, rubbers and oil-soluble materials for use as tacky adhesives or other adhesives, sealing agents, paints, inks, polyolefin films, plastic moldings and the like. Further, hydrogenated C9 petroleum resins are lighter in color, have less odor, and are higher in heat stability and weather resistance, than unhydrogenated C9 petroleum resins, dicyclopentadiene (DCPD) petroleum resins and C5 petroleum resins.
Although hydrogenated C9 petroleum resins have excellent properties as described above, there is a demand for further improvement in their color and stability characteristics such as thermal discoloration resistance and light resistance, in the fields where the color of resins is particularly important, such as the fields of sanitary applications, foods and clear sealants. Further, conventional hydrogenated C9 petroleum resins are highly fluorescent, and since fluorescent materials are suspected of being carcinogenic, reduction of florescence of hydrogenated C9 petroleum resins is also demanded.
Hydrogenated C9 petroleum resins can be improved in thermal discoloration resistance and light resistance and reduced in fluorescence by, for example, adding increased amounts of generally used additives, such as antioxidants and UV absorbers. However, this technique is economically disadvantageous since these additives are expensive. Further, addition of an increased amount of an antioxidant improves the thermal stability only to a limited extent and tends to impair the light resistance, hence undesirable from the viewpoints of performance characteristics and properties. Furthermore, although UV absorbers improve the light resistance and reduce the fluorescence, they are yellowish in color and thus impair the initial color of the resins.
Known substitutes for hydrogenated C9 petroleum resins include hydrogenated pure monomer resins prepared by hydrogenating aromatic pure monomer resins (resins obtainable by polymerizing aromatic pure monomers) such as low-molecular styrene resins, xcex1-methylstyrene resins and isopropenyltoluene resins. The hydrogenated pure monomer resins are light in color, excellent in thermal discoloration resistance and light resistance, and less fluorescent. However, low-molecular styrene resins are prone to have a molecular weight greater than ordinary C9 petroleum resins, and therefore tend to be less compatible with polymers and elastomers. Further, it is difficult to prepare hydrogenated xcex1-methylstyrene resins or hydrogenated isopropenyltoluene resins, since decomposition reaction is likely to proceed during hydrogenation, due to the methyl group present at the xcex1-position of the benzene ring. Moreover, all of the above resins are prepared from highly purified monomers, and thus are expensive and unsuitable for practical use.
The main object of the present invention is to provide a hydrogenated C9 petroleum resin. and a process for preparing the same, said hydrogenated C9 petroleum resin retaining characteristics of known hydrogenated C9 petroleum resins and being excellent in thermal stability and light resistance and remarkably low in fluorescence.
The present inventors conducted extensive research in view of the above problems, and found that thermal stability and other properties of hydrogenated C9 petroleum resins are adversely affected by polymerization catalysts (for example, a boron trifluoride phenol complex) used for preparation of C9 petroleum resins as the starting materials of hydrogenated C9 petroleum resins, or phenols used as molecular weight modifiers during polymerization. Based on this finding, they further found that hydrogenated C9 petroleum resins obtained by the processes described below accomplish the above object.
The present invention provides the following processes for preparing hydrogenated C9 petroleum resins, hydrogenated C9 petroleum resins obtainable by said processes, tackifier, additive for plastics, and adhesive composition.
1. A process for preparing a hydrogenated C9 petroleum resin, comprising hydrogenating a C9 petroleum resin obtained by polymerizing polymerizable monomers of a C9 fraction using a non-phenolic Friedel-Crafts catalyst in the presence or absence of a non-phenolic molecular weight modifier.
2. A process according to Item 1, wherein the non-phenolic Friedel-Crafts catalyst is boron trifluoride or a boron trifluoride ether complex.
3. A process according to Item 1 or 2, wherein the polymerizable monomers include up to 20 wt. % of a monomer fraction having a higher boiling point than indene.
4. A process according to any one of Items 1 to 3, wherein the polymerizable monomers include up to 20 wt. % of a monomer fraction having a higher boiling point than indene, at least 50 wt. % of vinyltoluene, and up to 20 wt. % of indene.
5. A process according to any one of Items 1 to 4, wherein the hydrogenation degree of the aromatic nuclei of the hydrogenated C9 petroleum resin is at least 50%.
6. A hydrogenated C9 petroleum resin obtainable by a process according to any one of Items 1 to 5.
7. A tackifier comprising a hydrogenated C9 petroleum resin according to Item 6.
8. An additive for plastics, comprising a hydrogenated C9 petroleum resin according to Item 6.
9. An adhesive composition comprising a tackifier according to Item 7 and a base resin for adhesives.
According to the process of the present invention, a hydrogenated C9 petroleum resin is prepared by hydrogenating a C9 petroleum resin obtained by polymerizing polymerizable monomers of a C9 fraction. The process of the invention can be carried out by following the steps of conventional techniques for preparing hydrogenated C9 petroleum resins, except that the C9 petroleum resin is one obtained using a non-phenolic Friedel-Crafts catalyst in the presence or absence of a non-phenolic molecular weight modifier. The non-phenolic Friedel-Crafts catalyst and non-phenolic molecular weight modifier are employed so that the C9 petroleum resin does not contain detectable amounts of phenols. Thus, the C9 petroleum resin may contain phenols in a proportion smaller than the detection limit. Phenols can be detected by, for example, a color test using iron (III) chloride (xe2x80x9cYukikagobutsu Kakuninhou (Organic Compound Detection Method) Ixe2x80x9d, Chap. 1, pp. 9-12).
Phenols usable as phenolic Friedel-Crafts catalysts or phenolic molecular weight modifiers include C6-C20 phenols having a xe2x80x94OH group in the molecule, such as phenol, and cresol, xylenol, p-tert-butylphenol, p-octylphenol, nonylphenol and like alkyl substituted phenols.
Any Friedel-Crafts catalysts free from phenolic components can be employed for preparation of the C9 petroleum resin for use in the invention, without limitation. Specific examples of such catalysts include boron trifluoride, boron trifluoride ethyl ether complexes, boron trifluoride butyl ether complexes, boron trifluoride acetic acid complexes, aluminum chloride, titanium tetrachloride, tin tetrachloride and like Lewis acids; and sulfuric acid, phosphoric acid, perchloric acid and like protonic acids. From the standpoint of industrial availability, boron trifluoride and boron trifluoride ethyl ether complexes are preferred. If a Friedel-Crafts catalyst containing a phenol, such as a boron trifluoride phenol complex, is used, the hydrogenated C9 petroleum resin obtained by hydrogenating the C9 petroleum resin has poor thermal discoloration resistance.
The C9 petroleum resin for use in the invention is prepared in the presence or absence of a non-phenolic molecular weight modifier. Accordingly, no phenols are used as molecular weight modifiers during preparation of the C9 petroleum resin. Further, in the steps other than the molecular weight modification step, phenols serving as molecular weight modifiers must not be added. However, molecular weight modifiers other than phenols may be used in the invention without limitation. Useful molecular weight modifiers include diethyl ether, tetrahydrofuran, acetone, DMF, ethyl acetate, ethanol, isopropanol, toluene, xylene, mesitylene and water. C9 petroleum resins obtained in the absence of a molecular weight modifier tend to have a higher molecular weight and a higher softening point than C9 petroleum resins obtained in the presence of a molecular weight modifier, but the molecular weight and the softening point can be controlled as desired by selecting suitable polymerization conditions and other factors.
The polymerizable monomers used as the starting materials of the C9 petroleum resin are those contained in a C9 fraction, i.e., a cracked oil fraction which is obtained by thermal cracking or catalytic cracking of naphtha and has a boiling point of about 140 to 280xc2x0 C. in atmospheric pressure. Specific examples of the polymerizable monomers include styrene, xcex1-methylstyrene, xcex2-methylstyrene, vinyltoluene, indene, alkylindene, dicyclopentadiene, ethylbenzene, trimethylbenzene and naphthalene.
The proportions of these polymerizable monomers for forming the C9 petroleum resin are not limited, but it is preferred to use a C9 fraction containing up to 20 wt. % of a monomer fraction having a higher boiling point than indene, so that the resulting hydrogenated C9 petroleum resin is further improved in heat stability and light resistance and reduced in fluorescence. It is more preferred to use a C9 fraction comprising up to 20 wt. % of a monomer fraction having a higher boiling point than indene, at least 50 wt. % of vinyltoluene, and up to 20 wt. % of indene. It is still more preferred to use a C9 fraction containing up to 15 wt. % of a monomer fraction having a higher boiling point than indene. Particularly preferred is a C9 fraction comprising up to 15 wt. % of a monomer fraction having a higher boiling point than indene, at least 52 wt. % of vinyltoluene, and up to 15 wt. % of indene. A C9 fraction comprising the polymerizable monomers in the above proportions can be obtained by suitably selecting the distillation conditions for preparation of the C9 fraction.
The proportions of the polymerizable monomers in the C9 petroleum resin can be calculated by any methods without limitation. Generally, however, the following method (1) or (2) is employed:
(1) The proportions (amounts) of monomers in the C9 fraction are calculated from the results of gas chromatography of the C9 fraction before Friedel-Crafts catalyst polymerization. Then, the proportions (amounts) of monomers remaining after polymerization of the C9 fraction are calculated from the results of gas chromatography of the liquid fraction remaining after polymerization (the fraction removed as unreacted components from the polymerized oil by distillation). The proportions of monomers in the liquid fraction are subtracted from the proportions of monomers in the C9 fraction, to thereby estimate the proportions of polymerizable monomers in the C9 petroleum resin.
(2) The C9 petroleum resin is subjected to pyrolysis gas chromatography to estimate the proportions of polymerizable monomers in the C9 petroleum resin.
The C9 petroleum resin can be prepared by conventional methods such as the following: 100 parts by weight of a C9 fraction (polymerizable monomers) is polymerized using about 0.01 to 5 parts by weight of a non-phenolic Friedel-Crafts catalyst at about xe2x88x9260xc2x0 C. to 60xc2x0 C. to obtain a polymerized oil, and about 0.1 to 20 parts by weight of a basic substance is added to 100 parts by weight of the polymerized oil, followed by neutralization reaction at 10 to 100xc2x0 C. Usable basic substances include calcium hydroxide, sodium hydroxide, potassium hydroxide and aqueous ammonium. The polymerized oil neutralized with the basic substance is washed with water, where necessary. Then, about 0.1 to 20 parts by weight of activated clay is added to carry out clay treatment at 10 to 100xc2x0 C. Thereafter, the activated clay is filtered off, and the polymerized oil was distilled to remove unreacted components, to thereby obtain a C9 petroleum resin. A molecular weight modifier, when employed, is used in a proportion of about 0.01 to 3 wt. % relative to the C9 fraction.
It is preferred that the C9 petroleum resin have a softening point of about 50 to 200xc2x0 C., so that the resulting hydrogenated C9 petroleum resin has properties of general hydrogenated C9 petroleum resins. The C9 petroleum resin preferably has a number average molecular weight of about 250 to 4000.
The hydrogenated C9 petroleum resin of the invention can be obtained by hydrogenating the above C9 petroleum resin by a conventional hydrogenation technique to a desired hydrogenation degree.
The C9 petroleum resin is hydrogenated at least to such an extent that 100% of its olefinic double bonds are hydrogenated. Hydrogenation of 100% of the olefinic double bonds means that no signal of an olefinic double bond is significantly observed at 4.5 to 6.0 ppm in proton NMR analysis.
The hydrogenation degree of the aromatic nuclei is not limited. Generally, however, the higher the hydrogenation degree is, the better the stability characteristics (such as thermal stability and light resistance) become. Also, a higher hydrogenation degree tends to result in reduced fluorescence. Therefore, the hydrogenation degree of aromatic nuclei is preferably at least 50%, so that a hydrogenated C9 petroleum resin can be obtained which has high stability and low fluorescence. The hydrogenation degree of aromatic nuclei can be calculated from the area of 1H-spectrum of aromatic rings appearing at about 7 ppm in 1H-NMR of the C9 petroleum resin and said area in 1H-NMR of the resulting hydrogenated C9 petroleum resin, according to the following equation:
Hydrogenation degree (%)={1xe2x88x92(spectrum area in hydrogenated resin/spectrum area in starting resin)}xc3x97100
The hydrogenation reaction is carried out in the presence of a hydrogenation catalyst under conditions suitable for hydrogenating the C9 petroleum resin to the above specified degree.
Usable hydrogenation catalysts include various known catalysts such as nickel, palladium, platinum, cobalt, rhodium, ruthenium and like metals, and their oxides and sulfides. These hydrogenation catalysts may be used as supported on porous carriers with large surface areas, such as alumina, silica (diatomaceous earth), carbon and titania. Among these catalysts, a nickel-diatomaceous earth catalyst is preferably used in the invention, from the standpoints of the cost and ease of attaining the above specified hydrogenation degree. The amount of the catalyst to be used is about 0.1 to 5 wt. %, preferably about 0.1 to 3 wt. %, relative to the C9 petroleum resin.
The hydrogenation reaction is carried out at a hydrogenation pressure of usually about 30 to 300 Kg/cm2 and at a reaction temperature of usually about 150 to 320xc2x0 C. Preferably, the hydrogenation pressure is about 100 to 200 Kg/cm2 and the reaction temperature is about 200 to 300xc2x0 C. If the hydrogenation pressure is less than 30 Kg/cm2 or the reaction temperature is lower than 150xc2x0 C., the hydrogenation is difficult to proceed. On the other hand, if the reaction temperature is higher than 320xc2x0 C., the softening point is liable to be lowered owing to decomposition. The reaction time is usually about 1 to 7 hours, preferably about 2 to 7 hours. For the hydrogenation reaction, the C9 petroleum resin is used as melted or dissolved in a solvent. Usable solvents include cyclohexane, n-hexane, h-heptane and decalin. The above-mentioned amount of catalyst and reaction time are applicable when the hydrogenation is carried out by batch reaction system. However, flow reaction systems (such as fixed bed reaction system or fluidized bed reaction system) can be also employed.
The softening point of the hydrogenated C9 petroleum resin thus obtained is usually about 50 to 200xc2x0 C., although depending on the intended use. The hydrogenated C9 petroleum resin preferably has a number average molecular weight of about 250 to 4000. The hydrogenated C9 petroleum resin may contain any of various additives. The additives may be added after preparation of the hydrogenated C9 petroleum resin, or during or after preparation of the C9 petroleum resin. Usable additives include, for example, antioxidants. Since antioxidants are not the molecular weight modifier defined in the present invention, the results of the invention are not defeated even if the hydrogenated C9 petroleum resin contains a hindered phenol antioxidant such as 2,6-di-t-butyl-p-cresol, stearyl-xcex2-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2xe2x80x2-methylenebis(4-methyl-6-t-butylphenol) or tetrakis-[methylene-3-(3xe2x80x2,5xe2x80x2-di-t-butyl-4xe2x80x2-hydroxyphenyl)propionate]methane.
Like conventional hydrogenated C9 petroleum resins, the hydrogenated C9 petroleum resin of the invention is excellent in tack, adhesion and compatibility, and is colorless, transparent, tasteless and odorless. The hydrogenated C9 petroleum resin of the invention is highly compatible with, for example, elastomers and plastics such as ethylene-vinyl acetate copolymers (EVA); amorphous poly-xcex1-olefin (APAO); natural rubbers (NR); styrene-butadiene rubbers (SBR); styrene-isoprene-styrene block copolymers (SIS); styrene-butadiene-styrene block copolymers (SBS); styrene-ethylene/butyrene-styrene block copolymers (SEBS), styrene-ethylene/propylene-styrene block copolymers (SEPS) and like triblock elastomers; polyethylenes; polypropylenes; polybutadienes; polystyrenes; AS resins, MS resins; polyphenylene ethers; norbornene open-ring polymers; and cyclohexadiene polymers. As described before, the hydrogenated C9 petroleum resin of the invention is excellent in various stability characteristics, in particular thermal stability and light resistance, and has remarkably low fluorescence.
The hydrogenated C9 petroleum resin of the invention can be applied in the fields where various hydrogenated petroleum resins (including hydrogenated C9 petroleum resins, hydrogenated C5 petroleum resins, hydrogenated DCPD petroleum resins, hydrogenated C9-DCPD petroleum resins and hydrogenated pure monomer petroleum resins), hydrogenated terpene resins, hydrogenated cumarone-indene resins, rosin derivatives or the like are employed. For example, the resin of the invention can be incorporated as a tackifier component into a base resin for adhesives (including tacky adhesives, sealing adhesives and the like). In particular, the resin of the invention is useful and effective as a tackifier for toiletry materials, sanitary materials, clear sealants, EVA hot melt adhesives, protective films, laminating adhesives for glasses and transparent plastics, and adhesives for glass interlayers. The resin of the invention is also useful as an additive for plastics such as polyolefin films or sheets, optical plastics and transparent plastics. Further, the resin can be utilized as an additive for rubbers, inks, paints, plastic moldings, sheets, films and foams. In such applications, the resin of the invention may be used as mixed with any of various other resins at a desired mixing ratio, and any of various additives such as antioxidants and UV absorbers may be added to the resin of the invention.
The hydrogenated C9 petroleum resin obtained by the process of the invention is excellent in tack, adhesion and compatibility, colorless, transparent, tasteless and odorless, like conventional hydrogenated C9 petroleum resins. Moreover, the hydrogenated C9 petroleum resin of the invention is improved in thermal stability and light resistance and remarkably reduced in fluorescence, even if it has a hydrogenation degree of aromatic rings equivalent to that of conventional hydrogenated C9 petroleum resins. Further, when the hydrogenated C9 petroleum resin of the invention is added as a tackifier to various resins, the resulting adhesive compositions or the like have equivalent tack or adhesion characteristics and improved thermal stability, as compared with adhesive compositions or the like comprising conventional hydrogenated C9 petroleum resins.
The following Examples and Comparative Examples are provided to illustrate the present invention in further detail, and should not be construed to limit the scope of the invention. In these examples, all parts are by weight.